The present invention relates generally to a multiple-cylinder piston type refrigerant compressor adapted for use, for example, in an automotive air conditioning system, and more specifically to an arrangement of a refrigerant gas intake passage leading to a suction chamber of the compressor for reducing the difference in the suction pressure of refrigerant gas drawn into respective cylinder bores of the compressor.
The present invention is applicable to a constant-displacement swash plate type compressor, as well as to a variable-displacement compressor equipped with a wobble plate disposed so as to change its angle of inclination relative to a drive shaft on which it is supported, as disclosed, e.g, in U.S. Pat. No. 5,056,416. For aiding in understanding of the present invention, reference is made firstly to FIGS. 7 and 8 showing a rear end portion of a conventional refrigerant compressor in transverse section and fragmentary longitudinal section, respectively.
The compressor includes a rear cylinder block 1 axially combined with a front cylinder block (not shown) to thereby form a cylinder block assembly having defined therein a plurality of axial cylinder bores 2 arranged around the central axis of the cylinder block assembly, one of which cylinder bores is shown in FIG. 8, each receiving therein a reciprocatory piston 7. A cylinder head or a rear housing 6 is bolted to the axial rear end of the cylinder block 1 with a valve plate 5 interposed therebetween. The cylinder head 6 cooperates with the valve plate 5 to form a discharge chamber 8 in the central region and a suction chamber 9 in the radially outer peripheral region of the cylinder head. The valve plate 5 has a suction port 3a and a discharge port 4 allowing communication between each cylinder bore 2 and the suction chamber 9 and the discharge chamber 8, respectively, and such communication is controlled by flexible reed type suction and discharge valves arranged on opposite sides of the valve plate 5. As shown clearly in FIG. 7, there is provided a refrigerant gas inlet 12 having formed therein a gas intake passage 13 in communication with the suction chamber 9 and connected to an evaporator (not shown) of the refrigeration system via an external conduit (not shown) through which a refrigerant gas under a suction pressure is supplied to the compressor. The discharge chamber 8 communicates directly with a delivery passage 11 bored in a refrigerant gas outlet 10 through which a refrigerant gas under a discharge pressure is delivered out of the compressor to a condenser (not shown) of the refrigeration system via an external conduit (not shown) connected to the gas outlet 10.
Though not shown in the drawings, the pistons 7 are driven to reciprocate in the corresponding cylinder bores 2 by a rotary swash plate (not shown) driven to rotate by a drive shaft (not shown) rotatably supported in the cylinder block assembly.
In operation of the above-described compressor, a refrigerant gas fed through the passage 13 is drawn into the suction chamber 9 and subsequently introduced through the suction ports 3a-3d in the valve plate 5 into the cylinder bores 2, in which the refrigerant gas is compressed by the reciprocating motion of the pistons 7. The compressed refrigerant gas is pumped out of the cylinder bores 2 through the discharge ports 4 into the central discharge chamber 8, from which the compressed gas is discharged out of the compressor through the delivery passage 11.
As seen from FIG. 7, the suction chamber 9 of this type of compressor is often configured in a complicated manner because of various restricting factors in the design of a compressor, so that the flow of refrigerant gas in the suction chamber is subjected to resistance and also the distances from the gas intake passage 13 to the respective suction ports 3a-3d are different. In such an arrangement of the suction chamber 9, the suction pressure of the refrigerant gas becomes lower at suction ports 3a-3d which are located further from the intake passage 13, as seen in the counter-clockwise gas flowing direction in the suction chamber 9 in FIG. 7, and, therefore, an appreciable suction pressure difference occurs from a pressure drop or loss between the suction port 3a which is positioned closest to the gas intake passage 13 and the suction port 3a which is located most remote therefrom. At a compressor speed of 3,000 rpm, for example, the pressure difference amounts to about 0.5 to 1 kg/cm.sup.2, with the result that the volumetric efficiency of the compressor is not only affected, but also the difference in the suction pressure causes pulsation of the refrigerant gas which in turn develops vibration and noise of compressor parts.